Why do notes sound bad close together? A concise overview of dissonance

...and that's why beat frequency ain't a thing.

It definitely is a thing. But the term frequency used here doesn't have the same meaning as magnitude response in the frequency domain. It's just a term being used to qualify this perception phenomenon because we hear amplitude rather than magnitude and phase. Did you actually read what you just linked?

Or, rather, it already is present in one or more of the combined frequencies. In the same sense as thousands of Michelangelo's Davids are already present in every marble quarry.

You make no sense whatsoever.

So what you're telling me is the 440A on my AM radio is not a frequency (defined as "... the number of occurrences of a repeating event per unit time" by Wikipedia, the free encyclopædia), but a series of volume envelopes loosely defined by period T=1/400 sec? Who knew :\

I see. I don't appreciate this kind of low-effort sarcasm, I'm trying to be of help. You do realize a signal has to undergo demodulation in order to be retrieved and listened back? This specific case can be thought as AM DSB-SC.
Anyways no, there is no 440 Hz frequency component on the AM signal. The 440 Hz is information coded in the side-bands of the AM signal which in turn needs to be demodulated so you get your 440 Hz whatever back.

/r/edmproduction Thread Parent Link - youtu.be